JPS5855834B2 - Low frequency sound generator - Google Patents

Abstract

A low-frequency sound generator for generating intense sound.It comprises a resonator (10). Pressurized gas is supplied to the resonator as pulses through a feeder (13). The sound generator comprises means for positive feedback of the sound pressure in the resonator to the feeder at a predetermined resonance frequency of the resonator but not at other frequencies.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low-frequency sound wave generator that generates sound waves with a maximum frequency of about 50 cycles, and more specifically, the present invention relates to a low-frequency sound wave generator that generates sound waves with a maximum frequency of about 50 cycles, and more specifically, the present invention relates to a low-frequency sound wave generator that generates sound waves with a maximum frequency of approximately 50 cycles.
The present invention relates to a low frequency sound wave generator comprising a supply device for supplying the pulsation of the resonator to the resonator.

It has been known that powerful pulsating low-frequency sound waves and vibrating low-frequency sound waves are useful as means for removing soot and the like adhering to boilers, blast furnaces, and the like.

However, the reality is that no suitable device has been provided so far.

The present invention was made in view of the current situation, and an object of the present invention is to provide a low-frequency sound wave generator that generates strong low-frequency sound.

The low frequency sound wave generator of the present invention includes an open resonator and a supply device that controls the supply of pulsating compressed gas to the resonator, and further includes a predetermined resonance for the resonator. Means are provided within the resonant tube for feeding back the frequency of sound waves to the feeder.

The present invention will be explained in more detail below with reference to the accompanying drawings.

As shown in FIGS. 1 to 4, the low frequency sound wave generator of the present invention has a resonance tube 10 with a constant diameter.

One end 11 of this resonance tube 10 is open and the other end 12 is closed.

The resonance tube 10 serves as the resonator, and a large number of standing waves are generated inside the resonance tube 10.

As is well known, each of these standing waves has an antinode at one end (opening section) 11 of the resonance tube 10, and a node at the other end (closed section) 12.

It is known that these standing waves satisfy the following equation (1).

■=λ(2n+1)/4 ・・・・・・・・・・・・
...... (1) Here, ■ is the length of the resonance tube 10, λ is the wavelength of the standing wave, and n is 0.1.2...
It is an integer value such as...

Depending on the value of n, the fundamental vibration (n=o), the first harmonic vibration (
n=1) A standing wave such as a second harmonic vibration (n=2) is formed.

In the case of fundamental vibration (n=0), from equation (1), λ=41
In the case of the first harmonic vibration (n=1), λ=4-1 from equation (1).

In the present invention, the length l of the resonance tube 10 is configured to be equal to the length H of the wavelength of the sound wave generated by the low frequency sound wave generator.

In this way, many standing waves are formed inside the resonance tube 10, so the air pressure inside the resonance tube 10 is constantly vibrating, and the amplitude of this vibration is maximum at one end (opening) 11 of the resonance tube 10. ing.

Furthermore, as is well known, the following relationship exists between the frequency f and the wavelength λ of a sound wave.

Here, C is the propagation speed of the sound wave.

As mentioned above, in the case of fundamental vibration, λ=41, so the frequency f of the sound wave with respect to fundamental vibration can be expressed by the following equation.

The propagation speed of sound waves is 340 m/sec at 20°C, and if the length of the resonance tube 10 is 5rrL, then f = 340.
/4°5, and 17 cycles are obtained as the fundamental vibration frequency f.

Therefore, by supplying air pulsations with a frequency of 17 cycles to the 5 m long resonance tube 10, a sound wave with a frequency of 17 cycles can be generated from the resonance tube jO.

When the temperature inside the resonance tube 10 changes, the propagation speed of the sound wave changes accordingly, and thereby the frequency of the sound wave changes according to equation (3).

At the other end (closed part) 12 of the resonance tube 10, there is a supply device 1 for controlling gas at a constant pressure to be supplied to the low frequency sound wave generator.
3 is provided.

Air is usually used as the gas for the low-frequency sound generator of the present invention, but inert gas or the like can also be used.

As shown in FIGS. 1 to 4, this supply device 13 is connected to the resonance tube 1.
It has a fixed part 14 which has a diameter smaller than 0 and is coaxially and cylindrically connected to the resonance tube 10.

A movable part 15 is provided in an axially sliding arrangement in engagement with this fixed part 14, which movable part 15 is provided with a control opening 16.

In addition, the fixed part 14 has two chambers 17A, as shown in the figure.
17B, the first chamber 17A is connected to the suction fan 18A, and the second chamber 17B is connected to the blower fan 1.
Connected to 8B.

As a result, the pressure in chamber 17A becomes lower than atmospheric pressure, and chamber 1
The pressure at 7B is higher than atmospheric pressure.

Each chamber 17A, 17B has an opening 19A, 19B, which allows the chamber 17A, 17B to have a movable portion 15.
is communicated with the inside of the movable part 15 via the control opening 16 depending on its position.

The movable part 15 has a membrane 20 that is engaged with the closed part 12 of the resonance tube 10, and the membrane 20 is configured to vibrate in response to the elastic force of the compression spring 210.

The elastic force of this compression spring acts on the entire surface of the membrane 20.

As shown in FIG. 2, in an equilibrium state, the pressure at the opening 12 of the resonance tube 10 is the same as the surrounding pressure, so the movable part 15 is moved so that the chamber 17A is isolated from the resonance tube 10 and the chamber 17B is held at a position where it is in communication with the resonance tube 10.

That is, the chamber 17A is kept in a state of non-communication with the resonance tube 10 because the opening 19A and the control opening 16 do not match and are blocked, whereas the chamber 17B is kept in a state of non-communication with the resonance tube 10 because the opening 19A and the control opening 16 do not match. is held in communication with resonance tube 10 to form a narrow opening 22 as shown in FIG.

Therefore, air (or other gas) at a constant pressure is supplied to chamber 1.
7B is supplied into the resonance tube 10 through the narrow opening 22 and the movable part 15, and at this time, low frequency sound waves are generated.

The sound waves generated in this way are transmitted to the closed part 12 of the resonance tube 10.
This pressure change changes the pressure at the movable part 15.
vibrate the membrane 20 provided thereon.

The frequency of this vibration similarly corresponds to the length of the resonance tube 10, since the sound waves generated within the resonance tube 10 have a frequency corresponding to the length of the resonance tube 10.

In addition, when the vibration of the membrane 20 generated in this manner ends, the movable portion 15 of the feeder 13 has a natural vibration frequency between the frequency of the fundamental vibration and the frequency of the first harmonic vibration.

When the pressure in the closed part 12 of the resonance tube 10 is at its maximum (pressure higher than atmospheric pressure), the movable part 15 moves to the right against the elastic force of the elastic spring 21 as shown in FIG. .

As a result, the communication path between the chamber 17B and the resonance tube 10 increases, and the pressure in the closed portion 12 of the resonance tube 10 further increases due to the action of the blower fan 18B.

Furthermore, when the pressure in the closed portion 12 of the resonance tube 10 is at its minimum (lower than atmospheric pressure), the movable portion 15 moves to the left as shown in FIG.

As a result, the communication path between the chamber 17B and the resonance tube 10 is cut off,
Instead, the chamber 17A and the resonance tube 10 come into communication, and this causes the pressure in the closed portion 12 of the resonance tube 10 to further decrease due to the action of the suction fan 18A.

As is clear from the above description, when the low frequency sound wave generator of the present invention is started, the movable portion 15 of the feeder 13 is in an equilibrium state along the line shown in FIG.

Next, when the suction fan 18A and the blowing fan 18B start, weak low-frequency sound waves are generated by the movement of gas within the resonance tube 10 due to the action of the resonance tube 10 and the membrane 20.

This weak low frequency sound wave causes repetitive movement of the movable part 15 in the axial direction.

As a result, the low-frequency sound waves within the resonance tube 10 turn into strong sound waves that persist after a certain period of time, and are emitted from the resonance tube 10.

FIG. 5 shows an embodiment in which the chamber 17A of the above-mentioned components of the present invention is removed.

Even if the chamber 17A does not exist, the basic operation is the same as in the above case.

In FIG. 5, the membrane 20 is screwed through an O-ring 23 between a shoulder 24 provided at the rear end of the resonance tube 10 and a bushing 26 screwed to an end cover 25.

A space 27 behind the membrane 20 is communicated with the atmosphere via a cylindrical socket 28 provided on the end cover 25.

These sockets 28 are covered by an auxiliary cap forming a cylindrical camp 29 and a complex passage 30, which extends into the rear space 27 of the membrane 20.
It connects the air and the atmosphere.

Incidentally, by forming such a complicated passage 30, it is possible to prevent dirt and the like from entering the space 27 behind the membrane 20.

A pipe 31 is connected to the end cover 25, and the rear end 32 is formed so that it can be connected to the blowing fan 18B or other suitable constant pressure fluid supply source.

Another part of the pipe 31 is a socket 33 connected within the resonance tube 10.

The movable part 15 is provided with a membrane 20, which movable part 15 is formed to slide over a socket 33,
Moreover, the socket 33 is closed at its inner end.

In addition, the socket 33 has a lateral hole 34 at its inner end so that communication within the resonant tube 10 is controlled via the lateral hole 34 with a constant pressure fluid supply.

Here, the horizontal hole 34 is an opening 19B shown in FIGS. 2 to 4.
This corresponds to

In this case, low-frequency sound waves are generated by operations exactly the same as those shown in FIGS. 1 to 4.

However, in this case, since there is no portion corresponding to the chamber 19A, the gas supplied from the fluid supply source will flow inside the resonance tube 10.

In some cases this is not very important, and in other cases it can be very advantageous.

A spring corresponding to the spring spring 21 is provided on the right side of the membrane 20, but the movable part 15 can also be returned by the inherent spring action of the membrane 20.

When the resonance tube 10 of the low frequency sound generator of the present invention is inserted into a boiler, a blast furnace, etc., the pressure inside these is usually higher or lower than atmospheric pressure.

Therefore, when the space 27 is communicated with the atmosphere by the means shown in FIG. 5, a difference occurs in the static pressure of the gas applied to both sides of the membrane 200.

As a result, the equilibrium position of the membrane 20 and the corresponding movable part 15 changes, so that the difference in the static pressure of the gas is compensated by the change in the position of the movable part 15.

FIG. 6 shows an example of preventing such compensation from being performed.

In FIG. 6, a socket 28 and a passage 30 for communicating the space 27 with the atmosphere are not provided, and instead, a pipe 36 is provided in the resonance tube 10.

This ensures that the same pressure is always applied to both sides of the membrane 200.

Since this pipe 36 is connected to the closed part of the resonance tube 10, which is a node of vibration of the sound wave, the pressure in the space 27 is reduced by the pipe 3.
It is not affected by the sound wave pressure in the resonance tube 10 via the resonance tube 6.

For the above reasons, the low frequency sound wave generator of the present invention shown in FIG. 6 does not cause any inconvenience even if it is placed in a gas having a pressure different from atmospheric pressure.

In the embodiment shown in FIG. 6, there is no direct communication between the outside air and the space 27, and the space 27 can be considered to be closed.

Therefore, the air inside the space 27 acts as a spring behind the membrane 20.

The spring action described above is thereby added to the natural spring action of the membrane 20, which in turn acts on the natural frequency of the moving system.

It is desirable that the membrane 20 of the low frequency sound wave generator of this invention be as thin as possible.

However, it is inconvenient that the film thickness is too thin and the spring constant becomes small.

If the membrane 20 is too thin, the spring constant will be too small in relation to the size of the membrane 20, and this will cause the natural frequency to become very small.

Furthermore, it is extremely difficult to produce a film that is thin and has a large spring constant.

In the embodiment shown in FIG. 6, the air cushion means a spring action due to the space 27.

) allows the use of membranes with low spring constants,
Furthermore, this air cushion has similar spring characteristics that cause the membrane 20 to vibrate inwardly and outwardly.

Although the thin membrane has different properties on the inner and outer sides, this does not affect the spring constant of the overall system to the same extent as if no air cushion were present.

This is because the spring action of membrane 20 accounts for only a small portion of the total spring action.

To explain by giving an example, in the embodiment of the low frequency sound wave generator of the present invention shown in FIG.
0, this membrane 20 has a spring constant of approximately 4000 ON/m.

On the other hand, if the space 27 has a volume of 24 liters, the air cushion of the air 27 in the embodiment shown in FIG. act.

If the total spring constant is approximately 4000 ON/m, the membrane 20 only occupies a small portion of the total spring constant.

FIG. 6 shows a practical improvement of the low frequency sound generator of the present invention, which has a pulsating compressed air supply 38 connected to the space 27.

When a low-frequency sonic generator is used for a soot-filled boiler or blast furnace, it will be operated intermittently.

In this case, when restarting the operation, the movable part 15 is connected to the socket 33.
Sometimes the top doesn't move.

This is especially likely to happen when the low frequency sound generator is used in a corrosive atmosphere.

As a result, the narrow opening in the horizontal hole 34 has a size of about 1 m11, and the weak sonic pressure generated by compressed air passing through this hole overcomes the residual frictional force of the movement system and causes the membrane to move. It is insufficient.

In this case, the sound wave generator may be activated using the pulsating compressed air supply 38.

That is, compressed air having a frequency substantially equal to the fundamental vibration of the sound wave generator is supplied to the space 27, thereby exciting the membrane 20.

FIG. 6 further discloses some equipment used in the low frequency sound generator of the present invention.

Air at a constant pressure is supplied from a suitable compressed air source 39 via a solenoid valve 41 to a conduit 40, which is likewise supplied via a solenoid coil 43 to a conduit 42, and further to the supply pipe 31 of the low frequency sound generator. It is supplied to the rear end 32.

In contrast, the conduit 42 is connected to a pulsating compressed air supply 38 .

This solenoid valve 41 is equipped with a throttle branch 44 .

A timer 45 is provided in the main body 46, and this timer 45 is electrically connected to each part as shown by chain lines.

Timer 45 is electrically connected to solenoid valves 41 and 43 to regulate the amount of compressed air sent to low frequency sonic generator and pulsating compressed air supply 38, respectively.

As described above, since the low frequency sound wave generator is operated intermittently, the operation time and stop time are adjusted by the timer 45.

Incidentally, when the valve 41 is open, it is in an operating state.

During the stop time, the valve 41 is closed and only a small amount of air is supplied via the throttle branch 44 to the low-frequency sound generator.

This small amount of air is used to cool the moving part 15 and the membrane 20 and also to protect the moving part 15 and the socket 33 from dirt.

In addition, the supply of this small amount of air causes the membrane 20 to vibrate minutely, making it easier to restart the low frequency sound generator.

As a result, the low-frequency sound generator is able to start operating under its own power, and when the valve 41 is opened, it can be used in a corrosive atmosphere and the moving parts 15 are affected. operation can be started immediately without the aid of a pulsating compressed air supply.

A probe 47 inserted into the space 27 is for sensing the vibration of the membrane 20, and is used to check the vibration of the membrane 20 when the valve 41 is open and the low frequency sound generator is in operation. .

When the probe 47 does not detect vibration of the membrane 20, the lamp 48 lights up.

In this case, the pulsating compressed air supply 38 is actuated by opening the solenoid valve 43, thereby providing the necessary start-up assistance and starting the operation.

According to the embodiment shown in FIG. 7, a conduit 40 is provided for supplying compressed air to the low frequency sound generator at the same time as the pulsating compressed air supply 38.

Compressed air is supplied to this conduit 40 via a solenoid valve 43, and this conduit 40 is further connected to a distributor 50.

The air supplied to the distributor 50 is then supplied to the tank 51 via the solenoid valve 52.

This tank 51 is connected to the space 2 like the solenoid valve 51.
It is located at 7.

An air flow passage 53 is provided between the tank 51 and the socket 33.

When the low-frequency sound generator is in operation, the solenoid valve 52 is open and compressed air for driving is supplied to the tank 51.
Supplied from.

In order to equalize the pulsation of the compressed air, a tube having a smaller diameter than that used when connecting the conduit 40 directly to the socket 33 is used as the conduit 40.

Compressed air is supplied to the tank 51 from the distributor 50 via an air flow passage and a regulating throttle valve 54, and this air flow passage is provided in parallel with the air flow passage 53 via a solenoid valve 52.

When the low frequency sound generator is stopped, the solenoid valve 52 is closed, but the membrane 20 and the movable part 15 remain in the tank 5.
1 and subsequently to the socket 33.

Such a modified embodiment is made possible by replacing it with an aperture branch 44 as shown in FIG.

In FIG. 7, the feeder is mounted separately in the resonance tube 10 as a unit 10'.

A similar configuration can also be adopted in the embodiments shown in FIGS. 5 and 6.

In all of the embodiments described above, the membrane 20 was mechanically provided directly on the movable part 15, but the present invention is not limited to this. For example, the membrane is provided between the membrane and the movable part. It may be provided in between by electrical, gaseous, fluid means, etc.

Furthermore, although the above embodiments disclose mechanical feeders and membranes, electro-mechanical means such as microphones may also be used.

In this case, place the microphone at the rear end (closed part) of the resonance tube.
X, z or In the embodiments described above, the movable part 15 was moved by the spring action of the membrane 20 or the combination of the spring action of the space 27 and the spring action of the membrane 20, but as shown in FIGS. A mechanical spring 21 may be provided on the right side of 20.

Furthermore, although a simple tube was used as the resonance tube, resonance tubes of other shapes, such as square resonance tubes and Helmholtz-type resonance tubes, can also be used.

As is clear from the above explanation, the low-frequency sound wave generator of the present invention is capable of generating powerful and sustained low-frequency sound waves, and is effective in cleaning soot, etc. from boilers and blast furnaces. It is something that works.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the outline of the low frequency sound wave generator of the present invention, and FIGS. 2 to 4 are enlarged explanatory diagrams of the feeder portion to explain the operating principle of the present invention. FIG. FIG. 6 is an explanatory diagram showing one embodiment of the present invention, and FIG. 7 is a partial sectional view showing another embodiment of the feeder. 10...Resonance tube, 13...Supplier, 1
5...Movable parts, 17A, 17B...
Chamber, 18A...Fan for suction bow, 18B...
...Blower fan, 20... Membrane 21...
・Elastic spring, 27... Space, 38...
Pulsating compressed air supply.

Claims (1)

[Claims] 1. A cylindrical resonator 10 that generates gaseous sound waves from its open end.
A supply device 13 for supplying pulsating compressed gas is attached to the closed end side of the resonator, and this supply device 13 is arranged so as not to be affected by the pressure of the compressed gas supplied to the resonator, and controls the flow of the compressed gas. It has a movable valve body 15, and a partition means 20 which is elastically reciprocatable in the resonator is integrally connected with the valve body 15 to form a movable unit, and the resonant frequency of the movable unit resonates. higher than the fundamental frequency of the resonator and lower than its first overtone frequency (resonator 1
The supply device 1 only at a predetermined frequency among the resonant frequencies of 0
A low frequency sound wave generator characterized in that the length of the resonator is determined so that the sound wave pressure in the resonator is fed back to the valve body 15 of No. 3. 2. The low frequency sound wave generator according to claim 1, wherein the reciprocating means is a membrane 20, and this membrane is connected to the valve body 15. 3. A low frequency sound generator according to claim 2, wherein the membrane is connected to the valve body 15 of the feeder by mechanical, electrical, gas or fluid means. 4. The low-frequency sound wave according to claim 2, 3, or 4, wherein the valve body has a sliding portion that slides, and this sliding portion is not affected by compressed gas. Generator. 5. Said sliding part moves axially through a pipe 33 extending into the resonator 10, and said pipe has at least one opening controlled by the sliding part for the supply of compressed gas. 6. The low frequency sound wave generator according to claim 4, wherein the valve body is formed in a part other than the detachable part and communicates with the supply device and the resonator. Claims 2 or 3 or 4 or 4, wherein the aperture 22 is arranged to hold the aperture 22 and is modulated by sound waves generated in the resonator by the supply of compressed gas. 7. The low frequency sound wave generator according to claim 5, wherein a space 27 is formed in the resonator between the membrane and the end cover 25 of the resonator. Generator. 8. The low frequency generator according to claim 1, wherein the resonator is provided with a supply device at one end thereof, and the reciprocating means is provided at an appropriate position on the other end side. Sound wave generator. 9. The low-frequency device according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7, wherein the resonator is a Helmholtz resonator. Frequency sound wave generator. 10. The low frequency sound wave generator according to claim 7, wherein the space communicates with the surrounding outside air. 11. The low frequency sound wave generator according to claim 7, wherein the space communicates with the surrounding outside air. 10. A low-voltage device as claimed in claim 10, defined by at least one socket 28 provided on the cover 25 and a convoluted passage 30 formed with the socket by a cap 29 covering the socket. 12. The low frequency sound generator according to claim 10, wherein the space communicates with the resonator 10 via a pipe 36. 13. The pulsating compressed air supply body 38 connects the space to the resonator 10. 14. The low frequency sound wave generator according to claim 7, wherein the low frequency sound wave generator supplies compressed air to the space at substantially the same frequency as the sound waves generated by the low frequency sound wave generator. The low frequency sound generator according to claim 7, further comprising a probe 47 for sensing the vibrating state and resting state of the membrane.15. 16. The low frequency sound wave generator according to claim 2, wherein a tank 51 is provided in the supply device, and compressed air is supplied to the valve body through the tank.16. The low frequency resonator according to claim 2 or 15 includes valves 41 and 52 for alternately supplying compressed gas directly to the resonator through throttle valves 44 and 45. Sound wave generator.